1,720,979 research outputs found
Fine-tuning of supramolecular selectivity in metal–salophen-based receptors
Full text linkIl progetto di ricerca portato avanti nei tre anni di dottorato si colloca nell'ambito della Chimica Supramolecolare, disciplina che riguarda lo studio delle interazioni deboli che portano alla formazione, in modo reversibile, di sistemi molecolari più complessi.
I complessi metallo-salofen (N,N’-bis(salicilidene)-1,2-fenilenediammina = salofen), che da tempo sono oggetto di studio nel laboratorio in cui ho svolto la tesi di dottorato, sono complessi metallici che consentono lo studio di fenomeni di riconoscimento molecolare che si basano su interazioni acido-base di Lewis.
Durante questi tre anni sono stati sintetizzati e studiati complessi salofenici dello zinco, del nichel, del palladio e del dicatione uranile.
Sono stati sintetizzati e caratterizzati recettori salofen-uranile decorati con anelli aromatici differentemente sostituiti. Attraverso studi di binding con sali di tetrabutilammonio TBAX (X- =Cl- ,Br- ) in cloroformio e acetonitrile è stata messa in luce la presenza di interazioni anione-π e l’influenza dell’ingombro sterico sulla selettività del riconoscimento, modulando l’accesso al sito di coordinazione. Sono state anche ottenute diverse strutture cristallografiche che provano senza ambiguità la presenza di interazioni anione-π fra tali recettori e vari alogenuri di tetralchilammonio. Questo progetto ha previsto la collaborazione con il gruppo di ricerca coordinato dal Prof. Kari Rissanen dell'Università di Jyväskylä (Finlandia). Nell’ultima parte di questo lavoro, sono stati sintetizzati e caratterizzati una serie omologa di complessi non simmetrici di salophen-uranile con anelli aromatici direttamente legati allo scheletro salofenico, aventi un unico sostituente in posizione para (N(CH3)2, OCH3, H, Br, NO2). Attraverso studi di binding con il sale di tetrabutilammonio cloruro TBAX (X- = Cl-) in acetonitrile, sono state ottenute buone correlazioni lineari di energia libera che supportano il fatto che anelli aromatici elettrondeficienti stabilizzano il complesso supramolecolare con l’anione grazie all’interazione anione-π, mentre anelli aromatici elettron-ricchi diminuiscono la costante di binding per effetti repulsivi in modo diametralmente opposto.
Complessi metallo-salofen di Zn, Ni, and Pd, sono stati ottenuti nello stato solido attraverso sintesi innescate solo da energia meccanica. La sintesi ti tali composti si è rilevata facile, veloce e senza l’uso di solventi. Infatti, la meccanochimica rappresenta una valida alternativa alle classiche sintesi basate su solventi organici spesso cancerogeni. I prodotti ottenuti sono stati studiati attraverso tecniche complementari nello stato solido: diffrazione a raggi X di polveri, diffrazione a raggi-X di cristalli singoli e spettroscopia NMR allo stato solido. Oltre a ciò, sono state ottenute quattro nuove strutture cristallografiche delle molecole sintetizzate. Questo progetto ha previsto la collaborazione con il gruppo di ricerca coordinato dal Prof. Wouters dell'Università di Namur (Belgio)
Chiese emiliane e storia sismica recente: un'indagine sull'(in)efficacia degli interventi pregressi
No full textThis research aims to analyze the strengthening interventions realized on churches after the 1996 earthquake in the Emilia area, in order to verify their real performance considering the damage suffered during the 2012 earthquake. In fact, both seismic events affected areas in the provinces of Reggio Emilia and Modena (in the North of Italy). In particular, this paper focuses on the analysis, at different scales, of two intervention typologies frequently adopted: tie-rod systems to prevent the overturning of the main facade and reinforced concrete slab for the consolidation of the vaults. For the evaluation of their effectiveness, a statistical analysis was carried out, at a territorial scale, through the design of a GIS database, and an in-depth analysis of three case studies
The Supramolecular Attitude of Metal–Salophen and Metal–Salen Complexes
Full text linkIn this review we cover some aspects of metal–salophen and metal–salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this last point has been only briefly mentioned
On the design of a low-cost racing car chassis
No full textTraditional chassis technologies still play an important role in the racing and sports car market. The design of such a specialist vehicle is a matter of finding a compromise between performance, safety and manufacturing costs. Performance mainly means a high torsional stiffness which directly affects the cornering behaviour of the vehicle. Safety issues regard the impact absorbing capability of the structure. On the cost side it should be underlined that racing cars are usually hand-made in very small numbers. The production of low power, low cost racing cars in particular is heavily affected by workmanship costs.
The paper aims to present a project currently under development at the University of Brescia with the co-operation of Metra, one of the leading European companies in the field of aluminium alloy extrusion. A single-seater chassis has been designed with the main target of matching reduced manufacturing costs with high safety and structural performance levels.
The chassis sidewalls are one-piece, closed section light alloy extrusions which provide bending and torsion stiffness as well as energy absorption properties for either front and side impacts. The two beams directly support the front suspension and engine. A casting and traditional steel tube rollbars connect the beams, together with a few honeycomb panels bonded into rails designed in the section. Purposely designed extrusions also replace traditional castings for components like wheel uprights and clutch bell allowing for relevant scale economy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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